U.S. patent application number 11/060465 was filed with the patent office on 2006-08-24 for architecture and provisioning tools for managed multicast virtual private lan trees.
This patent application is currently assigned to ALCATEL. Invention is credited to Bashar Said Bou-Diab, Bijan Raahemi.
Application Number | 20060187950 11/060465 |
Document ID | / |
Family ID | 36011004 |
Filed Date | 2006-08-24 |
United States Patent
Application |
20060187950 |
Kind Code |
A1 |
Bou-Diab; Bashar Said ; et
al. |
August 24, 2006 |
Architecture and provisioning tools for managed multicast virtual
private LAN trees
Abstract
Methods, tools, and a multicast connectivity architecture are
provided for provisioning bundled high bandwidth multi-channel
multimedia broadcast services over a packet switched communications
network. Multicast group membership join/prune requests generated
by the destination network nodes are processed on edge. Multicast
tree connectivity in the core of the communications network is
static and centrally provisioned based on multicast group member
edge network nodes associated with subscribers, while dynamic
multicasting techniques are employed over the distribution portion
of the service provider's communications network to deliver
requested content to each destination network node. The methods and
tools compute multicast trees, configure on-tree branching network
nodes, and establish Virtual Private LAN network overlays for
channel bundles to convey multi-channel content in the core of the
managed communications network between edge network nodes.
Centralized multicast tree provisioning enables the use of
efficient multicast tree topologies, while VPLS packet transport
provides interoperability between disparate Layer-2 packet
transport technologies employed in different portions of the
communications network.
Inventors: |
Bou-Diab; Bashar Said;
(Ottawa, CA) ; Raahemi; Bijan; (Ottawa,
CA) |
Correspondence
Address: |
KRAMER & AMADO, P.C.
Suite 240
1725 Duke Street
Alexandria
VA
22314
US
|
Assignee: |
ALCATEL
Paris
FR
|
Family ID: |
36011004 |
Appl. No.: |
11/060465 |
Filed: |
February 18, 2005 |
Current U.S.
Class: |
370/432 ;
370/390 |
Current CPC
Class: |
H04L 12/185 20130101;
H04L 45/48 20130101; H04L 45/16 20130101; H04L 12/1854
20130101 |
Class at
Publication: |
370/432 ;
370/390 |
International
Class: |
H04L 12/28 20060101
H04L012/28; H04J 3/26 20060101 H04J003/26 |
Claims
1. A method for provisioning broadcast services over a managed
packet switched communications network infrastructure, the method
comprising: a. provisioning a multicast tree in the core of the
managed communications network between an edge switching node
associated with a super-head end content source node and a
plurality of distribution edge switching nodes; b. distributing a
channel to the plurality of distribution edge switching nodes over
the provisioned multicast tree; c. each distribution edge switching
node intercepting membership change requests received from
destination nodes in the distribution portion of the communications
network, each membership change request specifying a channel; d.
the edge switching node establishing, over the distribution portion
of the communications network, a multicast tree branch between the
distribution edge switching node and the destination node from
which a join membership change request was received and forwarding
content of the specified channel over the established multicast
tree branch; and e. the edge switching node tearing down the
multicast tree branch between the distribution edge switching node
and the destination node from which a prune membership change
request was received, the interception and processing of membership
change requests at distribution edge switching nodes reducing
delays associated with establishing multicast tree branches to
destination nodes.
2. The method claimed in claim 1, wherein provisioning broadcast
services includes provisioning high bandwidth multi-channel
multimedia content.
3. The method claimed in claim 2, wherein each multimedia channel
is constituent of a channel bundle, the method comprising
distributing each multimedia channel bundle to the plurality of
distribution edge switching nodes over the provisioned multicast
tree.
4. The method claimed in claim 2, wherein each content channel is
constituent of at least one channel bundle and distribution edge
switching nodes hold information regarding channel bundles, and
information regarding user subscriptions to channel bundles, the
method comprising selectively establishing the multicast tree
branch to the destination node, if the user associated with the
destination network node subscribes to a channel bundle including
the specified channel.
5. The method claimed in claim 4, further comprising replicating
channel content to legitimate subscriber associated destination
nodes.
6. The method claimed in claim 1, further comprising source
filtering packets received from destination network nodes at
corresponding distribution edge switching nodes to filter out
illegitimate traffic.
7. The method claimed in claim 2, wherein prior to provisioning the
multicast tree the method further comprises centrally determining
the multicast tree based on: a specification of the bandwidth
required to convey the multi-channel multimedia content, the
network address of the edge switching node associated with a
super-head end content source node, the plurality network addresses
of the plurality of distribution edge switching nodes.
8. The method claimed in claim 7, wherein in centrally determining
the multicast tree, the method further comprises: a. obtaining
network provisioning and connectivity information; b. selecting a
multicast tree heuristics specification; and c. computing the
multicast tree based on the specified multicast tree
heuristics.
9. The method claimed in claim 8, wherein selecting the multicast
tree heuristics specification includes selecting of a Steiner tree,
a shortest path source tree, and a core based tree.
10. The method claimed in claim 8, wherein obtaining network
provisioning and connectivity information, the method comprises: a.
obtaining managed communications network infrastructure
connectivity information; b. obtaining status information regarding
managed network elements and interconnecting links; and c.
obtaining packet switching capacities of managed switching nodes
and transport bandwidth reservations on the interconnecting
links.
11. The method claimed in claim 10, wherein obtaining one of the
specification of the bandwidth required to convey the multi-channel
multimedia content, the network address of the edge switching node
associated with the super-head end content source node, the
plurality network addresses of the plurality of distribution edge
switching nodes, the connectivity information, status information,
packet switching capacities of managed switching nodes, and
transport bandwidth reservations on managed interconnecting links,
the method further comprises one of consulting network management
repository and receiving input from a user interface.
12. The method claimed in claim 8, wherein obtaining network
provisioning and connectivity information, the method comprises:
listening to the Interior Gateway Routing Protocol messages
exchanged in the managed communications network.
13. The method claimed in claim 7, wherein centrally determining
the multicast tree, the method further comprises: a. dividing the
plurality of managed switching nodes in the managed communications
network into a group of on-tree switching nodes and a group
off-tree switching nodes; and b. dividing the group of on-tree
switching nodes into a subgroup of branching switching nodes and a
subgroup of non-branching switching nodes.
14. The method claimed in claim 13, wherein provisioning the
multicast tree in the core of the managed communications network
between an edge switching node associated with a super-head end
content source node and a plurality of distribution edge switching
nodes, the method further comprising: a. configuring each on-tree
branching node with sub-tree connectivity information in accordance
with the determined multicast tree; and b. provisioning OSI Layer-2
tunnels between pairs of on-tree branching switching node and edge
switching nodes at transport capacities corresponding to the
aggregate transport bandwidth necessary to convey the multi-channel
multimedia content.
15. The method claimed in claim 14, wherein configuring a branching
network node with sub-tree connectivity information includes
providing the branching switching node with a switching table.
16. The method claimed in claim 15, wherein the switching table
includes an Ethernet VLAN switching table for switching multicast
packets between LSPs and between Ethernet links and LSPs.
17. The method claimed in claim 14, wherein the Virtual Private LAN
Service (VPLS) is employed to provision multicast tree
connectivity, the method further comprising: a. configuring each
on-tree branching node with VLSP sub-tree connectivity information;
b. provisioning VPLS pseudo-wires between pairs of on-tree
branching switching node and edge switching nodes; and c.
provisioning VPLS attachment circuits between the super-head end
source node and the associated edge switching network node, and
between each distribution edge switching node and each destination
node associated therewith, the provisioning of VPLS pseudo-wires in
accordance with the computed multicast tree reducing the need to
employ Split Horizon techniques.
18. The method claimed in claim 14, wherein provisioning OSI
Layer-2 tunnels between pairs of on-tree branching switching node
and edge switching nodes, the method includes provisioning OSI
Layer-2 Generalized MultiProtocol Label Switching (GMPLS) Label
Switched Paths (LSPS) therebetween.
19. The method claimed in claim 18, further comprising: a.
receiving at a branching switching node on the multicast tree, a
packet from a GMPLS LSP; b. terminating the packet's LSP header;
and c. Ethernet multicasting the packet to egress ports specified
in the sub-tree connectivity information.
20. The method claimed in claim 19, wherein the Ethernet
multicasting includes one of encapsulating the packet as an MPLS
packet for egress ports associated with MPLS LSPs in the multicast
tree and prepending the packet with an Ethernet VLAN header for
IEEE 802.1Q VLAN egress ports.
21. A system for provisioning broadcast services over a managed
packet switched communications network infrastructure, the system
comprising: a. a network management system for provisioning a
multicast tree over managed infrastructure in the core of the
managed communications network between an edge switching node
associated with a super-head end content source node and a
plurality of distribution edge switching nodes; b. distribution
edge switching nodes for: i. intercepting membership change
requests issued by destination nodes in the distribution portion of
the communications network; ii. establishing, over the distribution
portion of the communications network, a multicast tree branch
between the distribution edge switching node and the destination
node from which a join membership change request was received and
forwarding multimedia content of the specified channel over the
established multicast tree branch; and iii. tearing down the
multicast tree branch between the distribution edge switching node
and the destination node from which a prune membership change
request was received; and c. at least one source filter employed by
distribution edge switching nodes for filtering out illegitimate
membership change requests from destination network nodes.
22. The system claimed in claim 21, wherein in the provisioning of
broadcast services includes provisioning of high bandwidth
multi-channel multimedia content, intercepting membership change
requests comprising intercepting membership change requests
specifying a channel.
23. The system claimed in claim 21, further comprising a network
management repository for storing broadcast service provisioning,
network provisioning and connectivity information.
24. The system claimed in claim 22, wherein the network management
repository stores one of a specification of the bandwidth required
to convey the multi-channel multimedia content, the network address
of the edge switching node associated with the super-head end
content source node, a plurality network addresses of the plurality
of distribution edge switching nodes, status information, packet
switching capacities of managed switching nodes, and transport
bandwidth reservations on managed interconnecting links.
25. The system claimed in claim 22, further comprising a user
interface for specifying broadcast service provisioning, network
provisioning and connectivity information.
26. The system claimed in claim 25, wherein the user interface is
used for specifying one of the bandwidth required to convey the
multi-channel multimedia content, the network address of the edge
switching node associated with the super-head end content source
node, a plurality of distribution edge switching nodes, status
information, packet switching capacities of managed switching
nodes, and transport bandwidth reservations on managed
interconnecting links.
27. The system claimed in claim 21, wherein provisioning the
multicast tree the system further comprising means for obtaining
heuristics for determining a multicast tree.
28. The system claimed in claim 27, further comprising means for
determining the multicast tree.
29. The system claimed in claim 28, further comprising messaging
means for configuring branching switching nodes on the determined
multicast tree with sub-tree connectivity information; and
messaging means for provisioning OSI Layer-2 tunnels between pairs
of on-tree branching switching node and edge switching nodes at
transport capacities corresponding to the aggregate transport
bandwidth necessary to convey the content.
30. A multicast connectivity provisioning application for
provisioning broadcast services over a managed packet switched
communications network infrastructure, the application comprising:
a. distribution edge switching node selection means for selecting a
plurality of distribution edge switching nodes adapted to
selectively forward content to associated destination nodes; b.
retrieval means for retrieving service provisioning, network
provisioning, and connectivity information from one of a network
management repository and a user interface; c. a multicast tree
heuristics selector for selecting multicast tree determination
heuristics; and d. multicast tree determination means for
determining a multicast tree between an edge switching node
associated with a super-head end content source node and the
plurality of distribution switching nodes in accordance with the
selected multicast tree heuristics based on the service
provisioning, network provisioning, and connectivity
information.
31. The application claimed in claim 30, wherein the broadcast
services include high bandwidth multi-channel multimedia broadcast
services.
32. The application claimed in claim 30, wherein the retrieval
means further comprises one of a distribution edge switching node
list retrieval routine for accessing the network management
repository to retrieve a list of distribution edge switching node
list, and OSI Layer-2 map display component displaying for
selection a plurality managed switching nodes on the user
interface.
33. The application claimed in claim 31, wherein each multimedia
channel is constituent of at least one channel bundle, the
application further comprising means for provisioning each channel
bundle over the determined multicast tree.
34. The application claimed in claim 30, wherein the multicast tree
heuristics selector is employed in selecting one of shortest path
source tree, core base tree, and Steiner tree heuristics.
35. The application claimed in claim 30, further comprising
messaging means for configuring branching switching nodes on the
determined multicast tree with sub-tree connectivity information;
and messaging means for provisioning OSI Layer-2 tunnels between
pairs of on-tree branching switching node and edge switching nodes
at transport capacities corresponding to the transport bandwidth
necessary to convey content.
Description
FIELD OF THE INVENTION
[0001] The invention relates to high bandwidth broadcast data
communications, and in particular to packet switched communications
network architectures for distributing high bandwidth broadcast
audio/video content.
BACKGROUND OF THE INVENTION
[0002] Trends in the field of communications lead towards the
provision of television broadcast services over data communications
networks, and in particular over packet switched communications
networks. This requires convergence between television content
broadcast technologies and packet transport technologies.
[0003] Current developments related to content broadcasting, have
largely concentrated on provisioning low bandwidth streaming
services over packet switched communication networks. Such recent
developments concern the efficient transport of relatively low
bandwidth audio streams end-to-end between communication network
nodes. The most notable developments for the purposes of the
present description, relate to means for distributing an audio
stream generated by a single source network node to multiple
listening destination network nodes. The following represent
current developments concerning streaming audio content
distribution over packet switched communications networks:
[0004] In order to provide content broadcasting, connectivity is
provided today via multiple unicast (point-to-point) connections
between a source network node and destination network nodes.
Although a multicast connection from a source network node to
multiple destination network nodes provides a more efficient
transport facility than the multiple unicast connections typically
used today, multicast connectivity is not widely adopted due to the
lack of multicast management and billing capabilities.
[0005] In a multicast connection, the constituent links form what
is know as a multicast tree. The most generic multicast tree
provides many-to-many connectivity, known as anycast, enabling
every network node registered with a corresponding multicast group
to communicate with every other network node registered in the same
multicast group. However, unidirectional media content
distribution, such as internet radio broadcast service provisioning
requires a one-to-many connectivity, known as single-source
multicasting. Broadcasting an media channel over a packet switched
communications may be accomplished by a media source announcing to
the network the existence of a multicast group and the prospective
listening destination network nodes joining in.
[0006] A multitude of multicast tree variants, such as: Shortest
Path Source Tree (SPT), Core-Based Tree (CBT), and Steiner Tree
(ST) have been studied, while only some of these multicast tree
variants have been deployed with various degrees of success in
provisioning audio streaming services.
[0007] As exemplary illustrated in FIG. 1, an exemplary SPT
multicast tree 102, provisioned in an exemplary provider
communications network 100, includes shortest path branches (heavy
arrows) between the content source network node 104 and destination
network nodes 106. To achieve connectivity, six physical links 108
(heavy arrows) interconnecting participating router data network
nodes 110 are utilized in the service provider's network 100. The
SPT tree is the most popular connectivity architecture for
intra-domain and inter-domain multicast routing and is being used
by Open Systems Interconnect (OSI) Layer-3 multicast routing
protocols such as: PIM (Protocol Independent Multicast), M-OSPPF
(Multicast Open Shortest Path First), etc. for low-bandwidth audio
streaming service provisioning (such as audio media).
[0008] A CBT multicast tree stems from a designated root core
router network node; the multicast tree branches representing
shortest paths form the root core router network node to network
nodes participating in the same multicast group. CBT trees have
limited application to and are best suited for inter-domain
multicast routing.
[0009] A Steiner multicast tree provides a theoretical minimum cost
multicast connectivity that could be established given a network
topology. Finding the Steiner multicast tree, given a network
topology and a subset of destination multicast group members, is an
"NP-complete" problem, however heuristics have been proposed to
find a constrained Steiner tree in polynomial time. FIG. 2 shows a
theoretical deployment of the same exemplary service employing the
same network architecture as shown in FIG. 1, however multicast
connectivity is theoretically provisioned employing a Steiner
multicast tree 112. It is apparent from FIG. 2 that only four
interconnecting links 108 (heavy arrows) would be necessary in the
service provider's network 100 to provision multicast connectivity
between the same participating network nodes 104/106, thereby
requiring the utilization of significantly less resources in the
provider communications network. Utilizing less resources is a
desirable characteristic of provisioned services employing Steiner
multicast trees, especially when considering that typical
deployment scenarios include many edge network nodes 110-E
participating in a multicast group.
[0010] It is expected that a long (multi-second) delay may be
incurred in accessing a live internet radio broadcast service and
receiving a live internet radio stream broadcasted over a packet
switched communication network using today's multicast group
membership management scheme. The long delay is incurred: as a new
join request to the multicast group propagates from the requesting
destination network node 106 towards the source network node 104,
as the join request is being processed by network nodes
provisioning the multicast tree, and as a new multicast tree branch
is being provisioned to the requesting destination network node
106. It is also possible that a similar delay can be incurred when
tuning to a new station in operating an Internet radio.
[0011] Developments towards video broadcast over packet switched
communication networks include Source Specific Multicast (SSM)
techniques which may be employed in connecting a single video
content source to multiple receiver network nodes. SSM techniques
mirror the above mentioned audio stream broadcasting techniques in
broadcasting video content from a single video stream source and
may incur long access delays. Access delays to a high bandwidth
video stream can be particularly long in a multi-hop distribution
network. The main cause of the long access delay is the time taken
by a join request to travel from the requesting destination network
node to a network node participating in the provisioning of the
multicast tree and the time taken to process the join request. In
processing a join request not only does a new branch of the
multicast tree has to be provisioned to the requesting network
node, but the new branch having sufficient bandwidth to convey the
audio/video content of the single channel has to be found in
real-time.
[0012] However, internet broadcast TV services require effective
delivery of video content from multiple video content channel
sources to multiple channel subscribers. The above mentioned
streaming content distribution scenarios are difficult to extend to
provision internet broadcast TV services. Difficulties exist in
provisioning high bandwidth internet broadcast TV services over
packet switched communication networks considering the expectation
of the user of such services to channel surf.
[0013] No successful large scale internet broadcast TV service
deployment is known to date. Currently Protocol Independent
Multicast/Source Specific Multicast (PIM-SSM) and MPLS Multicast
Tree (MMT) are being investigated as potentially viable
technologies, both of which are at the proposal stage. These
proposals ignore the multi-channel aspect of broadcast TV, and
concentrate on channel-by-channel content distribution wherein each
multicast group is defined on a per channel basis. PIM-SSM requires
that each channel change event include a prune request sent to the
nearest branching node of the multicast tree provisioning the
currently received channel, and a join request sent to the nearest
node on the multicast tree provisioning the new channel. MMT on the
other hand requires that the prune and join requests of each
channel change event be sent to a Network Information Management
System (NIMS) for processing. The above two mentioned proposals do
not address bandwidth search delays. PIM-SSM attempts to minimize
packet transmission delay from the source network node to the
destination network nodes and MMT attempts to reduce multicast
group membership state tracking at participating network nodes.
[0014] Both proposals are based on Open Systems Interconnect
Layer-3 Internet Protocol Multicast protocol (IP Multicast) which
specifies the details of the operation of router communications
network nodes required to provision multicast tree connectivity.
Recent trends, reflected in the IP Multicast protocol, have led to
intelligent networks wherein the aggregate operation of individual
network nodes is employed to provision network wide services.
Relevant advantages of IP Multicast intelligent networking include
the fact that router network nodes cooperate to provision simple,
not necessarily efficient, multicast trees without outside
intervention, and to re-route traffic around failed infrastructure
without outside intervention. However advantages of intelligent
networking may be only be derived to the extent to which router
network node specific solutions can be found such that desired
aggregate results are achievable.
[0015] For example, in order to compute multicast trees,
information about other participating network nodes, about
interconnecting links, and multicast group membership information
needs to be taken into account. The provision of a large number of
multicast services via a larger number of multicast groups for
content delivery to an even larger number of destination network
nodes requires a huge amount of information to be tracked at each
participating network node. Therefore only the simplest of
multicast trees, such as SPT and CBT, can be implemented based only
on information about neighboring router network nodes,
interconnecting links therebetween, and multicast group membership
information. It is understood that provisioning a Steiner tree for
internet broadcast TV services in accordance with intelligent
networking goals, not only is it required that every router network
node track information about every network node and every
interconnecting link in the communications network in which
connectivity is provisioned, but tracking complete subscription
information in respect of each channel is also required. Although
employing a Steiner tree would guarantee minimal transport
bandwidth/packet processing resource utilization, the bandwidth
required to autonomously track and store, network wide resource
utilization and complete channel subscription information at each
router network node prohibits the use of Steiner trees in
accordance with intelligent networking goals. The information
tracked by each router network node to provision a multicast tree
is generically referred to as multicast forwarding state
information.
[0016] The PIM-SSM proposal is published by the Internet
Engineering Task Force (IETF) as draft-ietf-ssm-arch-06.txt and is
included herein by reference. PIM-SSM uses IP Multicast and a
dynamic SPT that is recomputed with subscriber membership changes.
PIM-SSM addresses storage requirements at each router network node
on a multicast tree. In summary, PIM-SSM proposes tracking at each
router network node only two levels of multicast forwarding state
information regarding: the parent router network node and the
children router network nodes of the multicast tree for each
channel provisioned via the router network node. As PIM-SSM
requires per-channel multicast forwarding state information stored
in each network node employed in provisioning the multicast
connectivity, the memory storage requirement scales linearly with
the number of channels provisioned and is not therefore scalable
for a large number of channels. Moreover PIM-SSM still incurs an
unacceptable delay in executing subscriber membership change
requests in large multi-hop distribution networks as explained
herein above.
[0017] The following is extracted from the abstract of the MMT
protocol specification published on the internet by the IETF as
draft-boudani-mpls-multicast-tree-06.txt and is incorporated herein
by reference: "A multicast router should [track] forwarding state
[information] for every multicast tree passing through it. The
number of forwarding states grows with the number of [multicast]
groups. [A] new approach, the MPLS Multicast Tree (MMT), [is
presented] which utilizes MPLS LSPs between multicast tree
branching node routers in order to reduce forwarding state[
tracking] and enhance scalability. In [accordance with the
presented] approach only routers that are acting as multicast tree
branching node routers for a [multicast] group need to [track and
store] forwarding state[s] for that [multicast] group. All other
non-branching node routers simply forward data packets by traffic
engineered unicast routing using MPLS LSPs." The MMT scheme uses IP
Multicast forwarding at branching router network nodes and MPLS
LSPs to transport IP packets between branching nodes. In essence
physical multicast trees are mapped by the MMT protocol into a
higher level multicast tree having only branching router network
nodes tracking forwarding states which establish MPLS LSPs between
themselves via non-branching router network nodes which do not
track forwarding states.
[0018] The MMT solution has the following deficiencies preventing
the use thereof in deploying internet broadcast TV services:
[0019] MMT concerns dynamic IP multicast groups. In accordance with
the proposed MMT scheme, MMT compliant connectivity is provisioned
by an NIMS. As a multicast group is defined for each content
channel, each channel requires its own multicast forwarding states
to be tracked at every branching router network node. However,
group membership is not handled quickly enough at edge router
network nodes 110-E. The MMT requires IGMP and PIM to relay the
subscriber membership join and prune request to the NIMS. The NIMS
calculates the new multicast tree, re-constructs the multicast tree
by instructing branching router network nodes to establish LSPs,
and updates IP forwarding states for the IP multicast group before
each subscriber's membership change request is executed. A
significant delay is therefore incurred between the subscriber's
decision to join a particular channel and the time the subscription
to that channel is completed.
[0020] As MMT re-calculates the multicast tree for each group
membership change, MMT does not lend itself to the use of
computation intensive tree determination algorithms such as the
minimum-cost Steiner trees. Therefore practical MMT deployments
cannot employ the Steiner multicast tree topology nor benefit from
potential resource utilization optimizations.
[0021] As the number of multicast groups increases, the memory
required at each branching router node to store the forwarding
state information becomes very large. While the number of router
network nodes tracking forwarding states is reduced, the MMT
protocol does not reduce the forwarding state tracking burden for
branching network nodes.
[0022] All dynamic IP Multicast protocols in general, and in
particular PIM-SSM, share the above mentioned deficiencies with
MMT.
[0023] Static IP Multicast schemes propose the use of static
multicast trees for delivery of IP Multicast packets from a source
network node to all network perimeter nodes using IP multicast
routing. Static IP Multicast schemes propose preventing dynamic
group membership changes in the network core beyond the first hop
to deliver group membership change requests to a membership change
processing entity. IGMP is used to communicate and process group
membership changes at the first hop.
[0024] Whether dynamic or static, OSI Layer-3 IP Multicast-based
proposals require a lot of stack processing for each packet
conveyed. Stack processing negatively affects high bandwidth
broadcast over packet switched communications networks particularly
because of the large number of packets conveyed. In particular the
more involved the packet processing at intermediary network nodes,
the more delay and jitter is incurred by the packet stream. Large
delays and jitter further impact the quality of streaming services,
and to a lager extent high bandwidth services.
[0025] In provisioning Internet TV broadcast services, service
providers would prefer a manageable multicast solution
characterized by a minimum provisioning cost and a predictable
performance in terms of multicast bandwidth, delay, and jitter.
Changes to group memberships need to be executed as quickly as
possible in response to the subscriber's selection. For scalability
reasons, it is desired that the least amount of forwarding state
information be stored at router network nodes 110 in the provider
network 100. There therefore the above mentioned issues need to be
addressed.
SUMMARY OF THE INVENTION
[0026] In accordance with an aspect of the invention, a method for
provisioning high bandwidth multi-channel multimedia broadcast
services over a managed packet switched communications network
infrastructure is provided. A multicast tree is provisioned in the
core of the managed communications network between an edge
switching node associated with a super-head end content source node
and a multitude of distribution edge switching nodes. Each
multimedia channel is distributed to the multitude of distribution
edge switching nodes over the provisioned multicast tree. Each
distribution edge switching node intercepts membership change
requests received from destination nodes in the distribution
portion of the communications network. Each membership change
request specifies a channel. The edge switching node establish,
over the distribution portion of the communications network, a
multicast tree branch between the distribution edge switching node
and the destination node from which a join membership change
request was received and forwarding multimedia content of the
specified channel over the established multicast tree branch. And,
the edge switching node tears down the multicast tree branch
between the distribution edge switching node and the destination
node from which a prune membership change request was received. The
interception and processing of membership change requests at
distribution edge switching nodes reduces delays associated with
establishing multicast tree branches to destination nodes.
[0027] In accordance with another aspect of the invention, a system
for provisioning high bandwidth multi-channel multimedia broadcast
services over a managed packet switched communications network
infrastructure is provided. A network management system is employed
for provisioning a multicast tree over managed infrastructure in
the core of the managed communications network between an edge
switching node associated with a super-head end content source node
and a multitude of distribution edge switching nodes. Distribution
edge switching nodes are employed for intercepting membership
change requests issued by destination nodes in the distribution
portion of the communications network. Each membership change
request specifies a channel. A multicast tree branch is
established, over the distribution portion of the communications
network, between the distribution edge switching node and the
destination node from which a join membership change request was
received and multimedia content of the specified channel is
forwarded over the established multicast tree branch. The multicast
tree branch is torn down between the distribution edge switching
node and the destination node in response to a prune membership
change request received from the destination node. And, at least
one source filter is employed by distribution edge switching nodes
for filtering out illegitimate membership change requests from
destination network nodes.
[0028] In accordance with yet another aspect of the invention, a
multicast connectivity provisioning application for provisioning
high bandwidth multi-channel multimedia broadcast services over a
managed packet switched communications network infrastructure is
provided. Distribution edge switching node selection means are
employed for selecting a multitude of distribution edge switching
nodes adapted to selectively forward multimedia content to
associated destination nodes. Retrieval means are employed for
retrieving service provisioning, network provisioning, and
connectivity information from one of a network management
repository and a user interface. A multicast tree heuristics
selector is employed for selecting multicast tree determination
heuristics. And, multicast tree determination means are employed
for determining a multicast tree between an edge switching node
associated with a super-head end content source node and the
multitude of distribution switching nodes in accordance with the
selected multicast tree heuristics based on the service
provisioning, network provisioning, and connectivity
information.
[0029] One of the advantages of the proposed solution, includes
avoiding the use of complex IP multicast routing protocols to
employ simpler and more reliable network nodes while yielding an
improved manageability.
[0030] Another advantage of the proposed solution, includes
employing multicast tree topologies such as, but not limited to,
minimum cost Steiner trees previously not deployable due to
intensive computational requirements associated therewith.
Substantially static multicasting techniques are proposed wherein a
multicast tree having desired attributes, such as a
delay-constrained Steiner multicast tree, is computed and
established to deliver strict performance and QoS requirements.
[0031] As the proposed solution decouples group membership from the
multicast tree structure in a provider domain, a further advantage
is derived from allowing edge network nodes to quickly handle group
membership changes at the network periphery without affecting the
multicast network architecture provisioned in a service provider's
network between the source and edge network nodes.
[0032] A further advantage is derived from a high degree of
scalability provided by the aggregation of forwarding state
information for multiple internet multimedia broadcast content
channels as multiple multicast channels share the same multicast
tree.
[0033] In accordance with a further advantage, a strict Layer-2
Internet multimedia broadcast solution is provided including
versatile means for delivering content.
[0034] In accordance with yet another advantage, tracking
forwarding state information for multicast groups at core router
network nodes may not be necessary at all as Ethernet broadcast
within established Virtual Private LAN may provide sufficient
filtering, thereby achieving multicast with broadcast in a
constrained broadcast domain! The Virtual Private LAN connectivity
information specified at each core network node includes in the
port membership specification, for each multicast group, all ports
corresponding to multicast tree links to the upstream parent
network node and to downstream child network nodes.
BRIEF DESCRIPTION OF THE DRAWINGS
[0035] The features and advantages of the invention will become
more apparent from the following detailed description of the
exemplary embodiment(s) with reference to the attached diagrams
wherein:
[0036] FIG. 1 is a schematic diagram showing interconnected data
network elements provisioning multicast connectivity having a
broadcast architecture based on a shortest path source tree;
[0037] FIG. 2 is a schematic diagram showing network architecture
including communications network elements theoretically
provisioning multicast connectivity having a Steiner tree broadcast
architecture; and
[0038] FIG. 3 is a schematic diagram showing, in accordance with
the exemplary embodiment of the invention, interconnected
communications network elements provisioning multicast connectivity
for high bandwidth multi-channel content broadcast.
[0039] It will be noted that in the attached diagrams like features
bear similar labels.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0040] In accordance with an exemplary embodiment of the invention,
a multicast connectivity provisioning method is provided for
reducing the delay in establishing new tree branches to new members
of a multicast group. In particular, in provisioning high bandwidth
internet TV broadcast services, multi-channel video content is
distributed from a super-head end content source 304 over a service
provider's network 300 shown in FIG. 3, to multiple distribution
edge router network nodes 310-E. The proposal applies equally to
implementations in which a multicast group is defined: for each
video content channel, for the aggregate of all video content
channels, and for a subgroup of video content channels. The
availability of multi-channel content at distribution edge router
network nodes 310-E eliminates the need to provision bandwidth
across the provider communication network 300 in real-time in
response to each multicast group membership join request.
Furthermore the availability of multi-channel content at each
distribution edge router network node 310-E renders unnecessary the
propagation of multicast group membership join/prune requests to
network nodes 310 participating in the multicast tree 312.
[0041] In accordance with the exemplary embodiment of the
invention, edge router network nodes 310-E process all join/prune
requests on edge. Processing all join/prune requests on edge,
requires forwarding state tracking for each next-hop leading to a
destination network node 306 only in a single router network node
310-E, and in particular typically only in the edge router network
node 310-E with which the destination network node 306 typically
interacts for general access to the service provider's network 300.
In accordance with the proposed multicast architecture, each new
multicast tree branch is established only over the distribution
portion 301 of the service provider's network 300 which typically
includes a customer loop 318. Therefore, the provision of each
channel to each edge router network node 310-E and the processing
of join/prune requests on edge, enables very fast access times to
any content channel thereby supporting channel surfing. For
certainty, the invention is not limited to deployments in which
destination network nodes 306 connect directly to a distribution
edge router network node 310-E via a dedicated customer loop 318,
other exemplary deployments make use of auxiliary
aggregation/deaggregation equipment 320.
[0042] In accordance with the exemplary embodiment of the
invention, distribution edge router network nodes 310-E (320) only
keep track of forwarding state information regarding dependent
destination network nodes 306 served. Therefore the storage of
forwarding state information is distributed over all participating
edge router network nodes 310-E and the forwarding state
information is stored only once. Therefore, forwarding state
information storage requirements are reduced for all router network
nodes 310 in the core of the service provider's network 300.
[0043] It is recognized that the proposal to distribute every
channel, within a multicast aggregate, also know as a channel
bundle to each participating edge router network node 310-E,
requires high bandwidth utilization over interconnecting links 308
in the service provider's network 300.
[0044] In accordance with the exemplary embodiment of the
invention, the high bandwidth utilization over interconnecting
links 310 is addressed by employing optimum multicast trees such
as, but not limited to, the Steiner multicast trees. A service
provider operated Network Management System (NMS) 322, cognizant of
the underlying service provider's managed communication network
architecture, is configured with multicast group membership
information regarding edge router network nodes 310-E, computes an
exemplary minimum cost Steiner multicast tree for each channel
bundle between the edger router network node 310-E associated with
the super-head end network node 304 and the distribution edge
network nodes 310-E associated with the destination network nodes
306, and configures only branching core router network nodes 310 in
the service provider's network 300 with multicast forwarding state
information corresponding to the channel bundle. The NMS 322 is
used for operations management functions, tracking network element
states and interconnecting link states. As multi-channel content is
being conveyed from the super-head end content source 304 to every
participating edge router network node 310-E, destination network
node 306 multicast group join and prune requests are handled at the
edge router network nodes 310-E and are therefore not propagated
across the service provider's network 300.
[0045] Exemplary implementations are envisioned wherein, a
multicast group corresponds to a subgroup (bundle) of video content
channels, for example users subscribe to a premium sports channel
package in addition to the basic channel package. In accordance
with exemplary deployments, a channel may be part of more than one
bundle.
[0046] Prior to the provisioning of the high bandwidth
multi-channel internet TV broadcast services, the NMS 322 is
provided with characteristics of the multi-channel content to be
provisioned. Without limiting the invention, the NMS 322 is
provided with the following information for each channel bundle:
the aggregate transport bandwidth necessary to provision all the
channels in the channel bundle, and the edge network node
identifier of the edge router network node 310-E associated with
the super-head end source network node 304. Depending on the manner
in which the content stream of each channel is provided to the
service provider network, the channel identifiers of the channels
in each channel bundle may also be provided to the NMS 322. For
example, in accordance with a VPLS implementation, described in
more detail herein below, each channel content stream to be
uploaded by the source network node 304 via an attachment circuit
and the bundling information is used to group attachment circuits
together.
[0047] In accordance with the exemplary embodiment of the
invention, the NMS 322 either uses a routing protocol or is
configured with information regarding which subscriber destination
network node 306 is associated with which multicast group edge
router network node 310-E. Subscription information is used to
specify associations between destination network nodes 306 and
channel bundles. The NMS 322 computes the minimum cost Steiner
multicast trees based on multicast group membership information.
The computation of the minimum cost Steiner multicast tree at the
NMS 322 also takes into account packet switching capacities at
communications network nodes 310 and transport bandwidth
reservations on interconnecting links 108. Depending on the
subscriber/edge router network node associations and subject to
bandwidth being available in the core of the service provider's
network 300, the computed multicast tree may be used by multiple
channel bundles. For large subscriber communities associated with
edge router network nodes 306, statistically all channel bundles
are provisioned to each participating edge router network node
310-E. The computation of the minimum cost Steiner multicast tree
at the NMS 322 reduces multicast tree computation requirements at
core router network nodes 310 while reducing resource utilization
in the service provider's communication network 300.
[0048] The substantially static nature of the centrally provisioned
multicast tree enables managed manual optimization of traffic
routing wherein operations management personnel interacts with an
exemplary multicast tree provisioning application tool executing in
a network management and provisioning context as described herein
below.
[0049] It is recognized that a large number of packets is necessary
to convey the entire multi-channel video content. In accordance
with the exemplary embodiment of the invention, the processing of
the large number of packets is reduced by provisioning OSI Layer-2
multicast tunnel connectivity. An exemplary OSI Layer-2 multicast
tunnel connectivity may be derived from the use of the Virtual
Private LAN Service (VPLS) technology developed for providing OSI
Layer-2 connectivity across a provider communications network
between disparately connected Local Area Networks (LANs). VPLS uses
OSI Layer-2 Ethernet switching techniques for forwarding OSI
Layer-2 Ethernet encapsulated packets between geographically
disparate LANs which are members of the same VPLS context, and
MultiProtocol Label Switching (MPLS) for Ethernet packet transport
between the Ethernet switching nodes across a communications
network. By employing VPLS for high bandwidth content transport in
the service provider's network 300, not only is stack processing
reduced for each packet, but also the use of VPLS packet forwarding
techniques together with the centralized multicast tree
provisioning at the NMS 322 reduces reliance on the routing
functionality of the network nodes 310 in provisioning high
bandwidth multi-channel streaming video services. While, routing
functionality at edge network nodes 310-E is still desired for
functionality other than multicast tree provisioning, the network
nodes 310 will be referred to hereinafter, without limiting the
invention thereto, as core switching network nodes 310 and
distribution edge switching network nodes 310-E respectively. It is
typical for a larger number of network nodes to be considered in
establishing the Steiner multicast tree as there are more switching
network nodes 310 than routers in a typical communications network
300. The larger number of switching network nodes 310 is desired
particularly as core switching network nodes 310 tend to operate at
higher bandwidths.
[0050] VPLS packet transport techniques lend themselves very well
to the proposal presented herein as VPLS packet transport employs
pseudo-wires in the core of the service provider network 300 and
attachment circuits over the distribution portion 301 thereof. A
VPLS pseudo-wire is in essence an Ethernet tunnel typically
provisioned as a Layer-2 MPLS Label Switched Path (LSP). The use of
the MPLS protocol at Layer-2 provides a certain degree of
independence from the transport technology employed by the physical
service provider's network infrastructure while reducing stack
processing of packets. After the NMS 322 determines the multicast
tree, VLPS pseudo-wires are provisioned along the determined
multicast tree between branching core switching nodes 310 in the
multicast tree and between branching core switching nodes 310 and
edge switching nodes 310-E. The NMS 322 provides branching core
switching node 310 with sub-tree connectivity information
corresponding to the multicast tree, for each channel bundle, and
the desired bandwidth to be reserved for the Ethernet tunnels
between branching/edge switching nodes 310. The invention is not
limited to the use of the Steiner tree, in fact the NMS 322 may
determine any multicast tree for provisioning VPLS pseudo-wires
along therewith in the core of the service provider's network
300.
[0051] When MPLS is used to provide pseudo-wire connectivity, the
MPLS label is stripped off each packet at each core branching
switching node 310, and the packet is replicated in accordance with
the specified sub-tree connectivity information updated by the NMS
322 for each multicast group.
[0052] While the use of VPLS technology lends itself to the
proposal described herein, the invention is not limited to the use
of VPLS techniques. The centralized multicast tree provisioning
proposed enables employing other forms of Layer-2 packet tunnels.
As described above, at each edge or branching switching node 310
where the LSP is terminated, the MPLS shim header and lower layer
headers are stripped and the encapsulated Ethernet packet is
switched. The manner in which Ethernet packet is switched may also
be similar to the operation of a typical standard VLAN capable
Ethernet switch, where the switching function would inspect the
Ethernet header and would yield a group (one or more) of egress
MPLS LSPs, a group of Layer-2 tunnels, or a group of IEEE 802.1Q
VLAN ports. The Ethernet packet is replicated and each copy is
prepended with an MPLS shim header corresponding to the egress LSP
or Layer-2 tunnel identified, and sent out through corresponding
egress ports after prepending necessary lower layer headers.
Similarly, for each egress Ethernet VLAN port identified, the
Ethernet packet is replicated and sent out therethrough after
prepending necessary lower layer headers.
[0053] However, as the VPLS transport protocol provides
interoperability with most physical transport technologies employed
in the distribution portion 301 of the network, an abstraction is
made of the transport technology employed at the physical layer in
the distribution portion 301 of the service provider's network. In
view of the use of the centrally provisioned MPLS Layer-2 Ethernet
tunnels, the edge switching nodes 310-E, or adjunct network
elements associated therewith, are the only network nodes requiring
compliance with the VLPS transport protocol which greatly reduces
deployment costs in implementing the proposed solution.
[0054] In accordance with the exemplary embodiment of the
invention, a multicast services provisioning tool is provided.
Exemplary implementations of the provisioning tool includes an
application executing in an operations management context
associated with the NMS 322, the application facilitating the
creation of an effective VPLS network for high-bandwidth
multi-channel internet TV broadcast.
[0055] In an autonomous mode of operation, the provisioning tool is
configured with the identity of the plurality of content
distribution edge switching nodes 310-E that provides access to the
Internet TV broadcast service to at least one subscriber associated
with a corresponding destination network node 306. In a manual mode
of operation, operations management personnel interacts with a
human machine interface to: retrieve a list of edge switching nodes
310-E, and select a group of edge switching nodes 310-E. The NMS
322 will typically provide a schematic Layer-2 network map, having
a schematic representation much like the one shown in FIG. 3, from
which operations management personnel can select the edge switching
nodes 310-E. The selected distribution edge switching nodes 310-E
together with the edge switching node 310-E associated with the
super-head end source network node 304 are made members of a
specified multicast group. As multicast groups are defined for each
channel bundle, the process is performed in respect of each channel
bundle.
[0056] Either via a default setting in the autonomous case, or via
express operations management personnel selection, a multicast tree
type such as, but not limited thereto, Shortest Path Source Tree
(SPT), Core-Based Tree (CBT), Steiner Tree (ST), etc. is
selected.
[0057] The multicast tree between the multicast group members is
computed based on the heuristics of the selected multicast tree
type taking into account network provisioning information (node
packet switching capacities and transport bandwidth reservations on
interconnecting links) available to the NMS 322. Given the
multitude of active network nodes, the network interconnection
topology, capacities of interconnecting links, and the multicast
group member edge switching network nodes 310-E, the heuristics of
the selected multicast tree type are applied to determine a
multicast tree. In the process, the multitude of switching nodes in
the service provider's network 300 are categorized as "on-tree"
switching nodes 310 and "off-tree" nodes. The on-tree switching
nodes 310 can be categorized as either "branching" 310-B or as
"non-branching" switching nodes 310. The multicast tree
determination process also determines sub-tree connectivity
information for branching switching nodes 310-B.
[0058] In accordance with the exemplary embodiment of the
invention, due to the intended substantially static nature of the
multicast tree to be provisioned in the service provider's
communications network 300, operation management personnel is
further provided with means for manual multicast tree construction
and/or editing. Operation management personnel may select switching
nodes 310 and change their on-tree/off-tree designation, as well
the branching/non-branching designation. Further operation
management personnel is provided with means for editing sub-tree
connectivity information.
[0059] Based on the determined multicast tree, the NMS 322
configures branching core switching node switching entries with the
sub-tree connectivity information, and sends instructions for
provisioning MPLS LSPs between edge switching nodes 310-E and the
branching core switching nodes 310, and between pairs of branching
core switching nodes 310-B (it is possible for a tree branch to
extend between two edge switching nodes 310-E as shown in FIG. 3,
in which case an edge switching node 310-E is also a branching
switching node 310-B). The provisioned LSP capacities correspond to
channel bundle aggregate capacities.
[0060] In the process, the NMS 322 communicates to branching core
switching nodes 310-B their participation in a specific Virtual
Private LAN corresponding to the multicast group provisioned over
the computed multicast tree. Each branching switching network node
310-B is configured with sub-tree connectivity information for the
internet TV broadcast service.
[0061] As edge switching nodes 310-E do not forward multicast group
membership join/prune requests from destination network nodes 306,
the NMS 322 does not provide sub-tree connectivity information for
edge switching nodes 310-E unless the edge switching nodes 310-E
are also branching nodes 310-E for the core portion of the
multicast tree. In accordance with an exemplary implementation of
the exemplary embodiment of the invention, the edge switching nodes
310-E handle group membership join/prune requests from associated
subscribers (IGMP snooping is an example), replicate channel
packets, and transmit channel packets to legitimate receivers 306.
The Ethernet switching tables at edge switching nodes 310-E are
built automatically via Ethernet address learning and aging
functionality along with IGMP (Internet Group Membership Protocol)
snooping functionality in a manner similar to standard compliant
Ethernet switching functionality. Implementations are envisioned
wherein edge switching nodes 310-E implement traffic filters to
filter out illegitimate traffic from receivers.
[0062] VPLS functionality is also employed at edge switching nodes
310-E in connecting pseudo-wires on the core side, with attachment
circuits on the distribution side which may include protocol
conversion.
[0063] It is noted that the necessary processing at a branching
switching network nodes 310-B is strikingly similar to the
processing performed by currently deployed VPLS branching routers
with two main exceptions:
[0064] The first exception is that current VPLS/HVPLS
implementations specify only an Ethernet switching function between
customer domains connected via attachment circuits and provider
domains connected via pseudo wires. In accordance with an exemplary
implementation of the exemplary embodiment of the invention,
Ethernet packet switching using an Ethernet VLAN switching table is
proposed for connecting provider domain nodes via pseudo wires.
[0065] The second exception relates to the fact that current VPLS
implementations rely on a Split Horizon mechanism to avoid
duplication of broadcast traffic in a loop topology. In accordance
with the exemplary embodiment of the invention, a loop-less
multicast tree topology is employed as provided by the NMS 322
preventing duplication of broadcast traffic without employing Split
Horizon techniques.
[0066] For greater certainty, in accordance with the exemplary
embodiment of the invention, multicast Ethernet packets may,
without limiting the invention, be either sent to selected VPLS
ports by consulting an Ethernet VLAN multicast forwarding table; or
broadcasted to all VPLS ports, MPLS LSPs, other Layer-2 tunnels, or
VLAN ports, if a multicast forwarding state is not present. Such
proposed functionality is compatible with Ethernet switching
functionality not employing Split Horizon--the compatibility
enabling deployment on a large variety of communications network
equipment.
[0067] Extensive reference was made hereinabove to high-bandwidth
multi-channel internet TV broadcast services. It is understood that
the multi-channel aspect of the invention is not limited to TV
content channels only, content channels being understood to contain
multimedia content (streaming video, streaming audio, streaming
text, data, messaging etc.)
[0068] Extensive reference was made hereinabove to the use of the
MPLS protocol in providing packet transport in support of the
high-bandwidth multi-channel internet multimedia broadcast
services. It is understood that in practice the Generalized MPLS
(GMPLS) protocol is typically employed, GMPLS extending the label
switching functionality in employing data communications equipment
physically provisioning actual OSI Layer-1 connectivity; equipment
such as, but not limited to: Time Division Multiplexing (TDM)
multiplexers, Synchronous Optical NETwork (SONET) Add/Drop
Multiplexers (ADMs), optical (lambda) switches, spatial switches,
etc.
[0069] The accompanying diagrams and the above description refer to
destination network nodes 306 being associated with edge switching
nodes 310-E. It is understood that a destination network node 306
may not be associated physically with the subscriber loop 318, a
myriad of communications network equipment, including, but not
limited to: Customer Premise Equipment (CPE) high speed modems, CPE
routers, proxy servers, firewalls, LAN switches, etc. (not shown)
may be located in the Internet access path. It is further
understood that the edge switching nodes 310-E may in fact receive
multicast group membership join/prune requests from CPE routers,
proxy servers, firewalls, etc. which send the join/prune requests
on behalf of destination network nodes 306.
[0070] Moreover, in the above description, the operation of edge
router network nodes 310-E included the aggregation of uploaded
user traffic for transport over the service provider's
communication network 300 and the deaggregation of download traffic
for distribution to respective destination network nodes 306. In
accordance with another exemplary implementation of the exemplary
embodiment of the invention, the edge switching nodes 310-E do not
perform aggregation/deaggregation functionality and the
distribution portion 301 of the service provider communication
network 300 includes aggregation/deaggregation equipment 320. In
accordance with such a deployment, multicast group membership
join/prune requests are processed at the aggregation/deaggregation
equipment 320 in accordance with dynamic multicast techniques. The
aggregation/deaggregation equipment 320 replicates channel packets,
and transmits channel packets to legitimate receivers 306.
Implementations are envisioned wherein traffic filters to filter
out illegitimate traffic from receivers 306 are implemented by the
aggregation/deaggregation equipment 320.
[0071] The embodiments presented are exemplary only and persons
skilled in the art would appreciate that variations to the above
described embodiments may be made without departing from the spirit
of the invention. The scope of the invention is solely defined by
the appended claims.
* * * * *